Introduction
Natural Selection - process by which populations become adapted to the environment. The fitness of an individual is measured by how well its offspring reproduce - i.e. how many offspring that survives and reproduce does an individual produce? Charles Darwin studied and closely watched peppered moths in their natural habitat. The peppered moths are light colored with darker areas of color. Like humans, however, these moths can be found in a range of pigmentation from very black to very white and all shades in between.
The different colored moths all belong to the same species; they reproduce with each other, and the color difference depends primarily on alternate alleles for a single gene. The black moths were presumably produced by mutation: biochemical change in DNA that makes up the genes for a trap. In pre-industrial England, tree trunks were gray. Gray moths are well camouflaged on gray tree trunks; black moths stand out. It has been shown experimentally that in areas with gray tree trunks, black moths are much more likely to be eaten by birds than are gray moths (presumably because black moths are much easier for the birds to see.) In industrial areas, because black moths avoided being eaten by birds, they survived better and therefore reproduced more (had higher fitness.) As a result, each generation, more and more of the offspring born came from black parents and inherited the black coloration, since the color differences between moths (gray versus black) are genetic.
Discussion
Darwin did many experiments to prove the evolution in the moths. He tested the chemicals in the soot to make sure that they were not causing a mutation in the moths. The chemical ratio was found to be higher than normal. Scientists concluded that it was mutation.
